HMC5983-DEM Datasheet, PDF (11/28 Pages) Honeywell Accelerometers – 3-Axis Digital Compass IC

HMC5983
Power Management
This device has two different domains of power supply. The first one is VDD that is the power supply for internal
operations and the second one is VDDIO that is dedicated to IO interface. It is possible to work with VDDIO equal to VDD;
Single Supply mode, or with VDDIO lower than VDD allowing HMC5983 to be compatible with other devices on board.
Communication Bus Interface
This device will be connected to a serial interface bus as a slave device under the control of a master device, such as the
processor. Control of this device is carried out via I²C or SPI interfaces. Use pin 6 (I²C /~SPI) to select between I²C and
SPI interface modes.
I²C Interface
This device is compliant with I²C -Bus Specification, document number: 9398 393 40011. As an I²C compatible device,
this device has a 7-bit serial address and supports I²C protocols. This device supports standard, fast, and high speed
modes, 100kHz, 400kHz, and 3400kHz, respectively. External pull-up resistors are required to support all these modes.
Activities required by the master (register read and write) have priority over internal activities, such as the measurement.
The purpose of this priority is to not keep the master waiting and the I²C bus engaged for longer than necessary.
SPI Interface
This device is compliant with both 4-wire and 3-wire SPI interface standards. Selection 3-wire mode is by setting SIM (SPI
serial interface mode selection) bit (MR2) in mode register to 1. See SPI Communication Protocol section later in this
datasheet for additional details.
Internal Clock
The device has an internal clock for internal digital logic functions and timing management. This clock is not available to
external usage.
H-Bridge for Set/Reset Strap Drive
The ASIC contains large switching FETs capable of delivering a large but brief pulse to the Set/Reset strap of the sensor.
This strap is largely a resistive load. There is no need for an external Set/Reset circuit. The controlling of the Set/Reset
function is done automatically by the ASIC for each measurement. One half of the difference from the measurements
taken after a set pulse and after a reset pulse will be put in the data output register for each of the three axes. By doing
so, the sensor’s internal offset and its temperature dependence is removed/cancelled for all measurements. The set/reset
pulses also effectively remove the past magnetic history (magnetism) in the sensor, if any.
For each “measurement”, the ASIC:
1. Sends a “Set” pulse
2. Takes one measurement (Mset)
3. Sends a “Reset” pulse
4. Takes another measurement (Mreset)
5. Puts the following result in sensor’s data output register:
Output = [Mset – Mreset] / 2
Charge Current Limit
The current that reservoir capacitor (C1) can draw when charging is limited for both single supply and dual supply
configurations. This prevents drawing down the supply voltage (VDD).
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